Apparatus for uninterruptedly supplying power including an electrical machine and a flywheel

ABSTRACT

An apparatus for uninterruptedly supplying power includes an electrical machine including a rotor and being designed and arranged to be connected to a load to be supplied with alternating current. Coupling units include a differential transmission including three input/output shafts. A flywheel is designed and arranged to store kinetic energy and to be connected to the rotor by the coupling units. Control units include a controllable brake and at least one electrical auxiliary machine to be operated as a motor. The electrical auxiliary machine and the controllable brake engage the third input/output shaft. The control units keep the number of rotations of the electrical machine approximately constant when the electrical machine is operated as a generator by kinetic energy being stored in the flywheel. The control units are being designed and arranged to operate the electrical auxiliary machine as a motor to realize a desired final number of rotations of the flywheel during operation of the electrical machine as a motor.

FIELD OF THE INVENTION

The present invention relates to an apparatus for uninterruptedlysupplying power including an electrical machine including a rotor andbeing operable as a motor or as a generator, the electrical machinebeing connected to a load to be supplied with alternating currentwithout a converter having a variable feed frequency being arranged inbetween, a flywheel being coupled to the rotor by coupling units havinga variable ratio of transmission, and control units for the transmissionof the coupling units, the control units at least in a certain range ofthe number of rotations of the flywheel keeping the number of rotationsof the electrical machine being operated as a generator constant by thekinetic energy being stored in the flywheel.

BACKGROUND OF THE INVENTION

Apparatuses for uninterruptedly supplying power serve to compensateespecially short-term failures of a power network. Generally and alsohereinafter, they are often called UPS systems. Usually, the powernetwork is used to supply a load with alternating current. It is a knownconcept to operate an electrical machine as a motor in addition to theload by means of the power network. The electrical machine affects aflywheel in a way to reach a certain number of rotations, and it keepsthe flywheel at this number of rotations. In case the network fails, thekinetic energy being stored in the flywheel may be used to operate theelectrical machine as a generator to supply the load with alternatingcurrent. Consequently, the kinetic energy of the flywheel and its numberof rotations decrease. When the flywheel is fixedly coupled to thegenerator, a converter having a variable feed frequency has to bearranged between the generator and the load to feed the load withalternating current at a constant frequency. Especially in the mediumvoltage range of approximately 10.000 volt, such a converter, as well asa d.c./a.c. converter that would have to be arranged after a directcurrent machine as electrical machine, is a complex unit when it is tobe designed for greater capacities, meaning for greater currents.However, even if it is designed for greater capacities, it is extremelysensitive to short circuit currents.

It is known to design an apparatus for uninterruptedly supplying powerin which the flywheel is not fixedly coupled to the rotor of theelectrical machine, but instead by coupling units having a variabletransmission. In a concrete known apparatus for uninterruptedlysupplying power by the firm HOLEC/HITEC, the coupling units include anelectromagnetic clutch being arranged between the electrical machine andthe flywheel. The electromagnetic clutch enables the flywheel todecelerate without the number of rotations of the electrical machinebeing operated as a generator decreasing. In case of a simple structureof the electromagnetic clutch, this is possible as long as the number ofrotations of the flywheel is more than the desired constant number ofrotations of the generator. In this case, it is necessary that theflywheel be accelerated by the electrical machine being operated as amotor via a different torque transmission path to reach a greater numberof rotations than the number of rotations of the electrical machine.When the electromagnetic clutch is desired to also allow for anincreasing transmission of the respective driving feed number ofrotations, the design of the electromagnetic clutch and the design ofthe required control units is especially complicated.

It is also known from prior art UPS systems to provide a combustionengine for longer-term failures of the network to operate the electricalmachine as a generator when longer-term power failures have to becompensated. The rotor of the electrical machine is connected to thegenerator by an overrunning clutch or a by a switchable clutch. When noconverter having a variable feed frequency is arranged after theelectrical machine, the number of rotations of the combustion enginemust have already reached the number of rotations of the electricalmachine before it may be coupled to the electrical machine. Then, thenumber of rotations has to be kept constant.

An electrical generator arrangement is known from U.S. Pat. No.4,278,928. A differential transmission in the form of a planetarytransmission is arranged to precede the input shaft of an electricalgenerator. The input shaft of the generator is connected to the sunwheel of the planetary transmission. The cage rotor of the planets ofthe planetary transmission is connected to the input shaft of the entireelectrical generator arrangement. The gear rim of the planetarytransmission may be driven at different numbers of rotations by ahydraulic drive to vary the ratio of transmission of the planetarytransmission such that the number of rotations of the generator is keptconstant even when the number of rotations at the input shaft of theentire electrical generator arrangement changes. The hydraulic mediumfor the hydraulic drive is provided by pumps that are driven by theinput shaft of the generator rotating at a constant number of rotationsor by a different element of the generator.

SUMMARY OF THE INVENTION

The coupling units include a differential transmission including threeinput/output shafts and that the control units include an electricalauxiliary machine being operable as a motor and a controllable brake,the electrical auxiliary machine and the controllable brake engaging thethird input/output shaft of the differential transmission, wherein thecontrol units are designed in a way that the auxiliary machine may alsobe operated as a motor to reach the desired final number of rotations ofthe flywheel when the electrical machine is operated as a motor.

In the novel UPS system, the flywheel is connected to the rotor of theelectrical machine by a differential transmission. A differentialtransmission means a mechanical transmission including threeinput/output shafts of which at least two are not coupled to oneanother. The differential transmission is used as a transmission havinga variable ratio of transmission by an electrical auxiliary machinebeing operable as a motor and a controllable brake both engaging thethird input/output shaft of the differential transmission. By means ofthe auxiliary machine, additional kinetic energy is stored in theflywheel during operation of the electrical machine as a motor. Duringoperation of the electrical machine as a generator, the number ofrotations of the electrical machine may be kept constant by means of thecontrollable brake at least until the number of rotations of the thirdinput/output shaft of the differential transmission has decreased toreach zero.

Typically, the capability of the auxiliary machine in the novel UPSsystem is substantially less than the capability of the electricalmachine.

For example, the differential transmission of the novel UPS system maybe a mechanical differential transmission or a planetary transmission.

In a preferred embodiment of the novel UPS system, the differentialtransmission is designed as a planetary transmission including a sunwheel, a cage rotor carrying planetary wheels and a gear rim. The sunwheel is fixedly connected to the input/output shaft leading to theflywheel and the cage rotor is fixedly connected to the input/outputshaft leading to the electrical machine. The gear rim is coupled to theinput/output shaft leading to the auxiliary machine at a fixed ratio oftransmission. In case of this arrangement, the planetary transmissionserves for a transmission of the number of rotations of the motor into agreater transmission of the number of rotations of the flywheel to storeas much kinetic energy as possible in a flywheel having a given momentof inertia. This transmission is further increased with the electricalauxiliary machine by driving the gear rim in an opposite direction.During the use of the energy of the flywheel, the electrical energy thathas been produced by the auxiliary machine to increase the transmissionof the planetary transmission is recovered. The electrical energy isrecovered except a small portion thereof that has been converted toheat.

The controllable brake may be an additional mechanical brake. However,the electrical auxiliary machine may instead be designed to be operableas an electromagnetic brake. The brake consumes the power that has beenproduced in the auxiliary machine or it may be used as emergency power.

In the simplest case, the electrical auxiliary machine is anasynchronous machine that is directly connected to be power network bythe control units when it is operated as a motor. An asynchronousmachine as auxiliary machine is to be combined with an additionalcontrollable brake. When the number of rotations of the thirdinput/output shaft of the differential transmission has been reduced toreach zero—while the asynchronous machine typically has been switchedoff—the control units may connect the asynchronous machine to theelectrical machine being operated as a generator with a polarity beinginverted compared to the network operational mode to accelerate thethird input/output shaft of the differential transmission in an oppositesense of rotation. The exact control of the number of rotations forkeeping constant and the number of rotations of the electrical machineis again achieved by means of the mechanical brake.

When the electrical auxiliary machine is a synchronous machine that isconnectable to the electrical machine and to the load by a converter,the auxiliary machine may be operated as the brake or at least toprovide a portion of the braking effort. The power that is produced inthe auxiliary machine while braking may be fed to the load by theconverter such that the electrical energy is not lost. Furthermore, theuse of the synchronous machine with the converter makes it possible totheoretically use the kinetic energy of the flywheel until its number ofrotations has reached zero. This means that the kinetic energy of theflywheel may be fully used. In the lower range of numbers of rotationsof the flywheel, it is necessary to operate the electrical auxiliarymachine as a motor at a sense of rotation being opposite compared to theone in the network operational mode. This serves to maintain the numberof rotations of the rotor of the electrical machine. The electricalmachine being operated as a motor by the electrical auxiliary machineprovides the required energy. In this way, the electrical auxiliarymachine compensates the energy balance except the power loss. Only aportion of the total power flows through the converter being locatedbetween the electrical auxiliary machine and the electrical machine andthe load, respectively. Consequently, the converter has a substantiallysimpler design compared to one used for an electrical machine that isoperated at a variable number of rotations.

The electrical auxiliary machine may also be designed as a directcurrent machine that is connectable to the electrical machine and to theload by a converter. In this case, the same operational modes arepossible as it is the case with an asynchronous machine including aconverter.

Usually, the electrical machine of the novel UPS system is a synchronousmachine having a simple design at low costs although it is verypowerful.

In addition to the flywheel being provided to compensate short-termpower failures with its kinetic energy, the rotor may be drivable by acombustion engine to compensate long-term power failures. A clutch beingswitchable by the control units may be arranged between the rotor andthe combustion engine.

It is especially preferred to arrange a differential transmissionbetween the rotor and the combustion engine. The differentialtransmission is provided in addition or alternatively to the switchableclutch. The third input/output shaft of the differential transmission iscoupled to another electrical auxiliary machine of the control units.The additional auxiliary machine serves to compensate differencesconcerning numbers of rotations of the rotor with respect to thecombustion engine, especially when the combustion engine has not yetreached its final number of rotations. The final number of rotations ofthe combustion engine is either approximately identical to the number ofrotations of the rotor, or it is related thereto with a fixed ratio.

In a further developed embodiment, the combustion engine does notrequire a starter motor since the differential transmission is arrangedbetween the combustion engine and the rotor. The energy being necessaryto start the combustion engine is then provided by the electricalmachine in combination with the additional auxiliary machine and,finally, by the flywheel.

However, it is also possible to arrange an overrunning clutch betweenthe rotor and the combustion engine. In this case, a separate startermotor for the combustion engine is required.

In the novel UPS system, the running up of the electrical machine into arange of numbers of rotations in which it is operable as a synchronousmotor may be realized by means of the electrical auxiliary machinewithout an additional motor. The flywheel may be kept still. Otherfeatures and advantages of the present invention will become apparent toone with skill in the art upon examination of the following drawings andthe detailed description. It is intended that all such additionalfeatures and advantages be included herein within the scope of thepresent invention, as defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingdrawings. The components in the drawings are not necessarily to scale,emphasis instead being placed upon clearly illustrating the principlesof the present invention. In the drawings, like reference numeralsdesignate corresponding parts throughout the several views.

FIG. 1 shows the general arrangement of the structural components of thenovel apparatus for uninterruptedly supplying power in a firstembodiment.

FIG. 2 shows a single line flow diagram being directed to the novelapparatus for uninterruptedly supplying power in the embodimentaccording to FIG. 1.

FIG. 3 shows the general arrangement of the structural components of asecond embodiment of the novel apparatus for uninterruptedly supplyingpower.

FIG. 4 shows the general arrangement of the structural components of athird embodiment of the novel apparatus for uninterruptedly supplyingpower.

DETAILED DESCRIPTION

The UPS system 1 (“UPS=Uninterruptible Power Supply”) includes anelectrical machine 2 in the form of a synchronous machine that may beoperated as a motor or as a generator. A rotor 3 of the electricalmachine 2 is fixedly connected to an input/output shaft 4 of adifferential transmission 5 in this case being designed as a planetarytransmission. Another input/output shaft 6 of the differentialtransmission 5 is fixedly connected to a flywheel 7. A thirdinput/output shaft 8 of the differential transmission 5 is connected tothe rotor of an electrical auxiliary machine 9 at a fixed ratio oftransmission. The input/output shaft 6 is connected to the sun wheel,the input/output shaft 4 is connected to the cage rotor of the planetarywheels and the input/output shaft 8 is connected to the gear rim of theplanetary transmission forming the differential transmission 5. In thisarrangement, the auxiliary machine 9 in this case being designed as anelectrical synchronous machine is controllable by a control unit 10 in away that the number of rotations of the input/output shaft 4 is keptconstant, even when the number of rotations of the flywheel 7 decreasesduring operation of the electrical machine 2 as a generator. The controlunit 10 determines the number of rotations of the input/output shaft 6by a sensor 24. The control unit 10 also serves to influence theflywheel 7 by a respective control of the electrical auxiliary machine 9in a way that the number of rotations is increased with respect to therotor 3 of the electrical machine 2 when the electrical machine 2 isoperated as a motor. This is done to store as much kinetic energy aspossible in the flywheel 7. The stored kinetic energy is available toovercome power failures of an electric network to which the UPS system 1is arranged parallel. For longer lasting power failures of the externalpower supply, a combustion engine 11 may be coupled to the rotor 3 ofthe electrical machine 2 by an overrunning clutch 12. The overrunningclutch 12 allows for a greater number of rotations, but not for a lowernumber of rotations of the rotor 3 with respect to the combustion engine11.

The single line flow diagram of FIG. 2 illustrates the power supply of aload 13 either by an external source of power 14 or by the electricalmachine 2. Typically, the external source of power 14 is a public powernetwork. In this case, a first switch 15, a tyristor switch 16 and athrottle 17 are arranged between the external source of power 14 and theload 13. The throttle 17 may also be connected in a known T-shapedmanner. In this case, the throttle 17 also has an effect on the powercoming from the electrical machine 2 to a desired extent. The electricalmachine 2 is connected between the throttle 17 and the load 13. Noconverter or d.c./a.c. converter is connected in between. However, aconverter 18 is located in front of the electrical auxiliary machine 9and the load 13.

In the following, different operational conditions of the UPS system 1according to FIGS. 1 and 2 will be explained based on a planetarytransmission i13=−2. The following table is a survey of the operationalmodes:

Generator Auxiliary Auxiliary Flywheel Flywheel Generator shaft drivedrive RPM Power RPM Power RPM Power Operational modes 1/min kW 1/min kW1/min kW 1 Normal condition, 4000 0 1500 0 333 0 the system is connectedto the power network 2 Unloading the flywheel I 4000 −1000 1500 761 333239 3 Unloading the flywheel II 3000 −1000 1500 1000 0 0 4 Unloading theflywheel III 2500 −1000 1500 1186 −167 −186 5 Loading the flywheel I2500 84.3 1500 −100 −167 15.7 6 Loading the flywheel II 3000 100 1500−100 0 0 7 Loading the flywheel III 4000 131.4 1500 −100 333 −31.4

1. Normal Operation

The system is connected to the power network.

During normal operation of the load 13 external source of power 14, theswitch 15 and the tyristor switch 16 are closed in the single line flowdiagram according to FIG. 2. The load 13, as well as the electricalmachine 2 being operated as a motor, is connected to the throttle 17.The power being consumed by the load 13, as well as the power loss ofthe electrical machine 2 and of the auxiliary machine 9, is completelytaken from the external source of power 14. A constant number ofrotations is introduced into the gear rim of the planetary transmissionby the auxiliary machine 9 to provide a constant ratio of transmissionof the input/output shafts 4 and 6 of the planetary transmission.

2. Unloading the Flywheel I

When the external source of power 14 fails, the energy that has beenstored in the flywheel 7 during normal operation according to 1 isrecovered. In this case, the switch 15 and the tyristor switch 16 areopened. In the example being illustrated in the above table, it isassumed that the load 13 has a demand for power of 1.000 kW. First, thepower is partially provided by the electrical machine 2 and by theelectrical auxiliary machine 9. Due to the branching concerning powerand moments in the planetary transmission, the electrical auxiliarymachine 9 is driven by the flywheel 7 to operate as a generator. Thenumber of rotations of the electrical auxiliary machine 9 continuouslydecreases in cooperation with the number of rotations of the flywheel 7.

3. Unloading the Flywheel II

Since the number of rotations of the electrical machine 2 being operatedas a generator is kept constant by the electrical auxiliary machine 9,an inversion of its sense of rotation and of the flow of power at theauxiliary machine 9 result when the number of rotations of theelectrical auxiliary machine 9 has reached zero.

4. Unloading the Flywheel III

Consequently, the auxiliary machine 9 has to be operated as a motor whenthe number of rotations of the flywheel 7 further decreases. Thenecessary energy is derived from the electrical machine 2 being operatedas a generator. Thus, the electrical machine 2 has to produce both thepower of the load and of the electrical auxiliary machine 9. However,this does not mean that additional power is taken from the flywheel 7since the power of the electrical auxiliary machine 9 is again availableto the electrical machine 2 at the side of its entrance.

5. Loading the Flywheel I

When the flywheel 7 is reloaded by the electrical machine 2 beingoperated as a motor, the sense of rotation of the electrical auxiliarymachine 9 is continuously inverted with respect to its prior sense ofrotations during the operation of the electrical machine 2 as agenerator. First, electrical energy is produced during the decelerationof the auxiliary machine 9, the electrical energy being provided to theload 13 and to the electrical machine 2 being operated as a motor,respectively, via the converter 18.

6. Loading the Flywheel II

After the number of rotations of the electrical auxiliary machine 9 hasreached the value of zero, again, the inversion of power and theinversion of the sense of rotation of the electrical auxiliary machine 9occur.

7. Loading the Flywheel III

Then, the final number of rotations of the flywheel 7 is reached by theelectrical machine 2, as well as the electrical machine 9 being operatedas motors. After the final number of rotations of the flywheel 7 hasbeen reached, only friction losses and similar power losses have to becompensated by the two electrical machines 2 and 9.

The embodiment of the UPS system 1 according to FIG. 3 differs from theone according to FIG. 1 in two aspects. First, the control unit 10 has amore complex design, and it additionally derives the number of rotationsof the input/output shaft 4 by an additional sensor 19. Another sensor20 is located at the output shaft of the combustion engine 11, and itsupplies the control unit 10 with the number of rotations of thecombustion engine 11. This arrangement is used by the control unit 10 toalso adjust the ratio of transmission of a further differentialtransmission 22 by a further electrical auxiliary machine 21. In thiscase, the differential transmission 22 is also designed as a planetarytransmission. The additional differential transmission 22 is locatedbetween a switchable clutch 23 and the combustion engine 11. The rotor 3of the electrical machine 2 is arranged at the other side of theswitchable clutch 23 being operated by the control unit 10. It ispossible to even out differences concerning the numbers of rotations ofthe combustion engine 11 and of the rotor 3 of the electrical machine 2.One reacts to very great differences concerning numbers of rotations, asthey for example occur during the standstill of the combustion engine11, by disengaging the clutch 23. For this purpose, the clutch 23 couldalso be designed as an overrunning clutch. It is even imaginable not toarrange the clutch 23 at all. However, in this case, the additionalelectrical auxiliary machine 21 has to reach a comparatively greatnumber of rotations during the standstill of the combustion engine 11,and the differential transmission 22 is permanently run which leads tofriction losses. When the planetary transmission 22 and the electricalauxiliary machine 21 are used, it is not necessary to arrange a separatestarter motor for the combustion engine 11. However, this arrangementresults in certain requirements for the control unit 10 to guaranteesynchronism of the rotor 3 of the electrical machine 2 at a constantnumber of rotations. In this case, it is not possible to use anoverrunning clutch 12.

Compared to the embodiment according to FIG. 3, the embodiment of theUPS system 1 according to FIG. 4 differs from the embodiment accordingto FIG. 1 with respect to different aspects. According to FIG. 4, theauxiliary machine 9 is designed as an electrical asynchronous machinethat is also operated as a motor by simply connecting it to the powernetwork when the electrical machine 2 is operated as a motor during thenetwork operational mode. During operation of the electrical machine 2as a generator, the auxiliary machine 9 of the embodiment according toFIG. 4 is simply switched off. The control of the third input/outputshaft 8 of the differential transmission 5 is then realized by aseparate mechanical brake 25. In this case, the mechanical brake 25includes a brake disc 26 being arranged on the shaft of the auxiliarymachine 9 and brake shoes 27 engaging the brake disc 26. The brake forceof the brake 25 is controlled by the control unit 10 in a way that thenumber of rotations of the input/output shaft 4 is kept constant untilthe number of rotations of the input/output shaft 8 has been reduced tozero by braking. In case kinetic energy is also to be taken from theflywheel 7 in the following, meaning when the number of rotationsfurther decreases, the auxiliary machine 9 may be connected to theelectrical machine 2 being operated as a generator with a polarity beinginverted compared to the network operational mode to now drive theinput/output shaft 8 in the opposite sense of rotation. The mechanicalbrake 25 again achieves the exact control of the number of rotations ofthe auxiliary machine 9 for keeping constant the number of rotations ofthe electrical machine 2. Contrary to the embodiments according to FIGS.1 and 3, in the embodiment according to FIG. 4, kinetic energy isconsciously consumed by the mechanical brake 25, meaning it is convertedto heat. Consequently, no power electronic for feeding back the powerthat has been produced by the auxiliary machine 9 is required.Furthermore, when an asynchronous machine is used as the auxiliarymachine 9, it is not necessary to use a converter for its operation as amotor. The embodiment of the UPS system 1 according to FIG. 4 isgenerally characterized by an especially low expenditure for the controlunit 10. Additionally, the embodiment is based on the use of anelectrical machine 2 of a common type at low costs, meaning one thatdoes not include a continuous input/output shaft 4. The combustionengine 11 may be coupled to the input/output shaft 4 by the overrunningclutch 12 and the gear wheels 28 and 29, as an example of a simplemechanical branching transmission. Due to the ratio of teeth of the gearwheels 28 and 29 and the ratio of transmissions of the branchingtransmission, respectively, different nominal numbers of rotations ofthe combustion engine 11 and of the electrical machine 2 may be takeninto account. FIG. 4 additionally illustrates in dashed lines a furtheralternative possibility of arranging the combustion engine 11 when anelectrical machine 2 of a standard design is used. However, when thecombustion engine 11 is coupled to the input/output shaft 6, there isthe disadvantage of the combustion engine 11 only affecting theelectrical machine 2 via the inert flywheel 7 when the combustion engine11 is desired to drive the electrical machine 2 as a generator.Consequently, the starting action of the combustion engine 11 to reachthe range of number of rotations of its nominal power is delayed.

Many variations and modifications may be made to the preferredembodiments of the invention without departing substantially from thespirit and principles of the invention. All such modifications andvariations are intended to be included herein within the scope of thepresent invention, as defined by the following claims.

What is claimed is:
 1. An apparatus for uninterruptedly supplying power,comprising: an electrical machine including a rotor and being designedand arranged to be operated as a motor and as a generator and to beconnected to a load to be supplied with alternating current without aconverter having a variable feed frequency being arranged between saidelectrical machine and the load; coupling units having a variable ratioof transmission and including a differential transmission, saiddifferential transmission including a first input/output shaft, a secondinput/output shaft and a third input/output shaft; a flywheel beingdesigned and arranged to store kinetic energy and to be connected tosaid rotor by said coupling units; and control units being designed andarranged for the transmission of said coupling units and including acontrollable brake and an electrical auxiliary machine being designedand arranged to be operated as a motor, said electrical auxiliarymachine and said controllable brake being designed and arranged toengage said third input/output shaft of said differential transmission,said control units being designed and arranged to keep the number ofrotations of said electrical machine constant at least in a certainrange of the number of rotations of said flywheel when said electricalmachine is operated as a generator by kinetic energy being stored insaid flywheel, and said control units being designed and arranged in away that said electrical auxiliary machine is operated as a motor toreach a desired final number of rotations of said flywheel when saidelectrical auxiliary machine is operated as a motor and that saidelectric auxiliary machine is continuously operated as a motor at fullspeed to maintain the desired final number of rotations of said flywheelas long as said electric auxiliary machine is operated as a motor. 2.The apparatus of claim 1,wherein said electrical auxiliary machine isdesigned and arranged to be operated as said controllable brake.
 3. Theapparatus of claim 1, wherein said electrical auxiliary machine isdesigned and arranged to be operated as said controllable brake.
 4. Theapparatus of claim 1, wherein said electrical auxiliary machine is anasynchronous machine.
 5. The apparatus of claim 1, further comprising aconverter being designed and arranged to connect said electricalauxiliary machine to said electrical machine and to the load, andwherein said electrical auxiliary machine is a synchronous machine. 6.The apparatus of claim 1, further comprising a combustion engine beingdesigned and arranged to drive said rotor.
 7. The apparatus of claim 6,further comprising a clutch being arranged between said rotor and saidcombustion engine and being designed and arranged to be switched by saidcontrol units.
 8. The apparatus of claim 7, further comprising a seconddifferential transmission and a second electrical auxiliary machine,said second differential transmission being arranged between said rotorand said combustion engine and said third input/output shaft of saidfirst differential transmission being coupled to said second electricalauxiliary machine.
 9. The apparatus of claim 8, wherein said combustionengine does not include a separate starter motor.
 10. The apparatus ofclaim 6, further comprising an overrunning clutch being arranged betweensaid rotor and said combustion engine.
 11. The apparatus of claim 10,further comprising a second differential transmission and a secondelectrical auxiliary machine, said second differential transmissionbeing arranged between said rotor and said combustion engine and saidthird input/output shaft of said first differential transmission beingcoupled to said second electrical auxiliary machine.
 12. The apparatusof claim 6, further comprising a second differential transmission and asecond electrical auxiliary machine, said second differentialtransmission being arranged between said rotor and said combustionengine and said third input/output shaft of said first differentialtransmission being coupled to said second electrical auxiliary machine.13. The apparatus of claim 12, wherein said combustion engine does notinclude a separate starter motor.